1. Field
Example embodiments of inventive concepts relate to storage systems, such as flash memory based storage systems and/or universal flash storage (UFS) systems.
2. Description of Conventional Art
A conventional storage system includes a host and a storage device. The host and the storage device may be connected through various interface standards. Power consumption of the storage system may be reduced using various methods.
One method for reducing power consumption is referred to as a HIPM (Host Initiate Power Management) method. In this example, if a host does not issue a command for a given time period (e.g., if the host is idle for given time period), then the storage device sets the storage device interface to a low-power state or a sleep state to reduce power consumption. The HIPM method, however, does not reduce power consumption in an active state when a command is being executed at the host.
Another method is referred to as a DIPM (Device Initiate Power Management) method. In this method, if the storage device interface of the storage device is idle for a given time period, then the storage device switches the state of the storage device interface to a low-power state or a sleep state. However, since firmware of the storage device and a command state of the host are not considered, the interface may enter a false sleep state. When in the false sleep state, the host or storage device waits due to entering into false sleep (e.g., until woken up) even though there is a command or data to be sent. This may result in consumption of unnecessary time and/or power due to the sleep and subsequent wakeup of the interface.
An idle time reference value may be increased to reduce the occurrence of the false sleep state. However, this results in an increase in an idle time when the interface is awake. Thus, power may still be unnecessarily consumed.
From a wakeup point of view, the above-described methods may start to wake up the interface when data or commands to be transferred through the interface exist. Although data or commands are ready to be sent, time and/or power may be consumed by a wakeup operation itself.